why the bad resolution (jaggies) on computer playback?

I've created a production shot on mini-DV, edited on PPro 1.5, exported with video set at 6.8 CBR and GOP at both 2,10 and 3,15. I authored in DWS2 where I set the audio to template, which was Dolby AC3, 192. The production has a number of effects done in AE and PPro that have slo-mo on them.

When playing back on a desktop and laptop using PowerDVD 6.0, these effects have "jaggies" appear on the movements, and a slight bit of this kind of pixelation appears when there's movement in the regular motion video. When playing back on a set-top DVD player over a t.v., none of these issues feel noticeable.

Can someone tell me why this is so, and if there's a way to correct for it?